Hydraulic valve with pressure limiter

Abstract

An assembly of valve sections includes an inlet section, an outlet section, a working section, and a working section. The working section is a conventional pressure compensated working section. The working section includes a directional control valve, a pressure compensator valve, and a pressure limiter valve. The valves are of integral construction, such that each is an essential part to complete the other. The pressure compensator valve includes a pressure compensator spool movable between an opened position and a closed position in response to a pressure differential across the spool. The pressure limiter valve includes a pressure limiter spool that moves to an open position to change the pressure differential and close the pressure compensator valve when a selected limit pressure is reached.

What is claimed is: 
     
       1. An integral pressure compensator valve and pressure limiter valve comprising:
 a fluid flow path; 
 a pressure compensator valve and a pressure limiter valve disposed in said fluid flow path and dividing said fluid flow path into an upstream side and a downstream side; 
 a pressure compensator spool carrying a pressure compensator valve surface, said pressure compensator valve surface being movable with said pressure compensator spool and defining a variable area fluid orifice in said fluid flow path; 
 a pressure limiter spool carrying a pressure limiter valve surface, a pressure limiter passage, said pressure limiter valve surface being movable longitudinally with said pressure limiter spool to open and close said pressure limiter passage, and 
 a housing for the fluid flow path, the pressure compensator valve and the pressure limiter valve, the housing having a first spool bore and the pressure compensator spool and the pressure limiter spool are disposed in the first spool bore, 
 wherein the pressure compensator spool includes a second spool bore, and the pressure limiter spool is slidably disposed in the second spool bore and is carried by the pressure compensator spool. 
 
     
     
       2. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , wherein said pressure compensator valve and said pressure limiter valve are coaxially disposed in said first spool bore. 
     
     
       3. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , wherein, said housing is one valve section of an assembly of valve sections in which each said valve section includes a main flow control valve and a work port, and each said main flow control valve is a directional control valve. 
     
     
       4. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 3 , wherein said housing of said one valve section includes a load sense passage. 
     
     
       5. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 4 , wherein said main flow control valve is in said upstream side of said one valve section. 
     
     
       6. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 5 , wherein said load sense passage hydraulically connects said compensator spool with the highest pressure level in all of said work port. 
     
     
       7. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , wherein said pressure compensator spool has at least one radial closing surface area exposed to fluid pressure at a location on said downstream side to urge said pressure compensator spool and said pressure compensator valve surface toward closed positions to close said orifice,
 said pressure compensator spool has at least one opening radial surface area exposed to fluid pressure at a location in said upstream side to urge said pressure compensator spool and said pressure compensator valve surface toward opened positions to open said variable orifice, 
 said pressure limiter passage establishes fluid pressure communication between a location in said fluid flow path and at least one said pressure compensator spool closing radial surface area, and 
 said pressure limiter spool has at least one opening radial surface area exposed to a limit fluid pressure to urge said pressure limiter spool and said pressure limiter valve surface toward their said opened positions to open said pressure limiter passage when said limit fluid pressure reaches a selected pressure level. 
 
     
     
       8. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 7 , including a first biasing device acting against said pressure compensator spool and biasing said pressure compensator spool and said pressure compensator valve surface toward their said closed positions, and a second biasing device acting against said pressure limiter spool and biasing said pressure limiter spool and said pressure limiter valve surface toward their said closed positions. 
     
     
       9. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , wherein said pressure compensator spool and said pressure limiter spool are disposed in a spool bore opening into said center spool gallery, and said pressure compensator valve surface and said pressure limiter valve surface are each exposed to fluid pressure in said center spool gallery. 
     
     
       10. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , wherein said pressure compensator valve includes a pressure compensator valve spring biasing said pressure compensator valve spool toward its said closed position and said pressure limiter valve includes a pressure limiter valve spring biasing said pressure limiter valve spool toward its said at rest position. 
     
     
       11. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 10 , wherein said pressure limiter spring acts between said pressure compensator spool and said pressure limiter spool. 
     
     
       12. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 1 , including a force transmitting spool, said force transmitting spool extending from said pressure compensator valve spring, through said pressure limiter valve spring, to said pressure limiter valve spool. 
     
     
       13. A working section for a valve assembly comprising:
 a valve body having an inlet core, a spool gallery with a reduced fluid pressure that is less than the fluid pressure of the inlet core, and at least one work port; 
 a spool extending through at least a portion of the valve body and being movable relative to the valve body for controlling fluid flow from the inlet core to the spool gallery; 
 a compensator valve having a compensator spool separating the spool gallery and the at least one work port, the compensator valve being biased into a closed position and opening for regulating flow between the spool gallery and the at least one work port; and 
 a pressure limiter for limiting the pressure provided to the work port to a predetermined value, the pressure limiter operable to move the compensator valve toward the closed position when the work port pressure meets or exceeds the predetermined value by connecting fluid passages to direct the reduced fluid pressure from the spool gallery to an opposite end of the compensator spool. 
 
     
     
       14. The working section of  claim 13  wherein a load sense pressure and a compensator spring act to bias the compensator valve toward the closed position, pressure in the spool gallery moving the compensator valve to the open position, the pressure limiter, in response to the work port pressure reaching the predetermined pressure, increasing the fluid pressure acting to bias the compensator valve toward the closed position to a value approximately equal to fluid pressure in the spool gallery. 
     
     
       15. The working section of  claim 13  wherein the pressure limiter is integral with the compensator valve. 
     
     
       16. The working section of  claim 15  wherein the compensator valve includes a spool, the pressure limiter including a limiter spool that is located in the compensator and is movable relative to the compensator spool in response to pressure in the work port. 
     
     
       17. The working section of  claim 16  wherein the compensator spool includes the plurality of fluid passage. 
     
     
       18. The working section of  claim 13  wherein the opposite end of the compensator spool is always fluidly connected to a load sense pressure. 
     
     
       19. An integral pressure compensator valve and pressure limiter valve comprising:
 a fluid flow path; 
 a pressure compensator valve and a pressure limiter valve disposed in said fluid flow path and dividing said fluid flow path into an upstream side and a downstream side; 
 a pressure compensator spool carrying a pressure compensator valve surface, said pressure compensator valve surface being movable with said pressure compensator spool and defining a variable area fluid orifice in said fluid flow path; and 
 a pressure limiter spool carrying a pressure limiter valve surface, a pressure limiter passage, said pressure limiter valve surface being movable with said pressure limiter spool to open and close said pressure limiter passage when a limit fluid pressure in the downstream side of the fluid flow path reaches a selected pressure level, 
 said pressure compensator valve surface exposed to said upstream side to urge said pressure compensator spool toward an opened position to open said variable orifice, 
 said pressure limiter passage establishes fluid pressure communication between the upstream side of said fluid flow path and at least one pressure compensator spool closing radial surface area for urging said pressure compensator spool closed when said limit fluid pressure reaches a selected pressure level. 
 
     
     
       20. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 19 , including a first biasing device acting against said pressure compensator spool and biasing said pressure compensator spool and said pressure compensator valve surface toward their said closed positions, and a second biasing device acting against said pressure limiter spool and biasing said pressure limiter spool and said pressure limiter valve surface toward their said closed positions. 
     
     
       21. An integral pressure compensator valve and pressure limiter valve as set forth in  claim 19 , including
 a control chamber exposed to fluid pressure at a location in said downstream side; and 
 a load sense passage connected to said control chamber, 
 wherein at least one said pressure compensator radial closing surface area is exposed to fluid pressure in said control chamber to urge said pressure compensator spool and said pressure compensator valve surface toward their said closed positions to close said variable orifice, and 
 wherein said pressure limiter passage establishes fluid pressure communication between said control chamber and a location in said upstream side of said fluid flow path, said housing includes a center spool gallery disposed in said fluid flow path between said main control spool and said integral pressure compensator valve and pressure limiter valve.